Method and system for fast inspecting defects

ABSTRACT

A method and system for inspecting defects saves scanned raw data as an original image so as to save time for repeated scanning and achieve faster defect inspection and lower false rate by reviewing suspicious defects and other regions of interest in the original image by using the same or different image-processing algorithm with the same or different parameters.

RELATED APPLICATION

This Application is a Divisional Application of U.S. application Ser.No. 14/268,213, filed on May 2, 2014, which is a Divisional Applicationof U.S. application Ser. No. 13/154,483, filed on Jun. 7, 2011, theentire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a method and system for inspectingdefects, and more particularly to a method and system for fastinspecting defects which decreases false rate of defect inspection.

Description of the Prior Art

Defect inspection in the semiconductor device has always been one ofimportant issues in semiconductor manufacturing process. Referring toFIG. 1, a conventional method for inspecting defects is achieved byobtaining a scanned image, e.g. an SEM (scanning electron microscope)image of a specimen such as a semiconductor device (S11) and identifyingdefects on the surface of the specimen within the scanned image (S12).Since the scanned data is of extremely enormous data volume and oftenlarger than 20 TB (tera-byte), the scanned data would be discarded afterdefect inspection (S13). In the case of requiring further verificationfor defects (S14), then return to step S11 and the specimen is rescannedfor defect analysis. Referring to FIG. 2, to be brief, the conventionalmethod for inspecting defects alternates between specimen scanning anddata analysis.

Some identified suspicious defects might be not real defects and a falserate is used for representing the accuracy of defect inspection. Thefalse rate has kept increasing due to sustained trend of minimizedsemiconductor manufacturing process and tremendously increased scanneddata. The false rate may be improved by enhancing scanning resolution ofE-beam inspection tools and rescanning all of regions of interest in thesame specimen; however, the scanning time and scanned data would begreatly increased due to the enhanced scanning resolution of E-beaminspection tools. In addition to increased inspection time, rescanningmight also encounter certain issues, such as missing real defects andmisjudging non-defects, caused by varied scanning conditions. Forexample, the charge condition of the surface of the specimen might bechanged at first E-beam scanning and results in variation in the scannedimage obtained at the second E-beam scanning and biased result of defectinspection.

To sum up, it is now a current goal to lower false rate of defectinspection.

SUMMARY OF THE INVENTION

The present invention is directed to a method and system for inspectingdefects which saves scanned raw data as an original image so as to savetime for repeated scanning and achieve faster defect inspection andlower false rate by reviewing suspicious defects and other regions ofinterest in the original image by using the same or differentimage-processing algorithm with the same or different parameters.

In first embodiment of the present invention, a method for fastidentifying defects includes scanning a specimen to generate an originalimage and locations of regions of interest and reviewing the locationson the original image to identify defects.

In second embodiment of the present invention, a method for decreasingfalse rate in defect inspection includes providing locations of regionsof interest of a specimen by scanning a surface of the specimen; savingscanned raw data as an original image; and reviewing the locations onthe original image to identify defects on the surface.

In third embodiment of the present invention, a method for fastinspecting defects includes scanning a surface of a wafer; identifyingsuspicious defects or critical patterns by using a firstimage-processing algorithm with a first set of parameters; savingscanned raw data from the scanning step as an original image;identifying hot spots according to the suspicious defects or thecritical patterns; marking locations of the hot spots; and reviewing thelocations on the original image to identify defects on the surface.

In fourth embodiment of the present invention, a computer readablemedium encoded with a computer program implementing a method for fastinspecting defects. The method comprises steps of scanning a surface ofa wafer; identifying suspicious defects or critical patterns by using afirst image-processing algorithm with a first set of parameters; savingscanned raw data from the scanning step as an original image;identifying hot spots according to the suspicious defects or thecritical patterns; marking locations of the hot spots; and reviewing thelocations on the original image to identify defects on the surface.

In fifth embodiment of the present invention, a system for fastinspecting defects includes a charged particle beam probe, a chargedparticle beam deflection module, an image forming apparatus, a storagemodule and a defect inspection module. The charged particle beam probegenerator is configured for generating a charged particle beam probe.The charged particle beam deflection module is configured for scanningthe charged particle beam probe across a surface of a wafer. The imageforming apparatus is configured for detecting secondary chargedparticles emitted from the surface of the region of interest beingbombarded by the charged particle beam probe and forming at least onescanned raw image accordingly. The storage module is configured forsaving the scanned raw image as an original image. The defect inspectionmodule encoded with a computer program is configured implementing amethod for fast inspecting defects. The method includes steps ofidentifying suspicious defects or critical patterns on the scanned rawimage by using a first image-processing algorithm with a first set ofparameters; identifying hot spots according to the suspicious defects orthe critical patterns; marking locations of the hot spots; and reviewingthe locations on the original image to identify defects on the surface.

The objective, technologies, features and advantages of the presentinvention will become apparent from the following description inconjunction with the accompanying drawings wherein certain embodimentsof the present invention are set forth by way of illustration andexample.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing conceptions and their accompanying advantages of thisinvention will become more readily appreciated after being betterunderstood by referring to the following detailed description, inconjunction with the accompanying drawings, wherein:

FIG. 1 is a flow chart schematically illustrating a method forinspecting defects according to a prior art;

FIG. 2 is a diagram schematically illustrating a method for inspectingdefects according to a prior art;

FIG. 3 is a flow chart schematically illustrating a method for fastidentifying defects according to an embodiment of the present invention;

FIG. 4 is a diagram schematically illustrating a method for fastidentifying defects according to an embodiment of the present invention;

FIG. 5 is a diagram schematically illustrating a plurality of examplesof critical pattern;

FIG. 6 is a flow chart schematically illustrating a method fordecreasing false rate in defect inspection according to an embodiment ofthe present invention;

FIG. 7 is a flow chart schematically illustrating a method for fastinspecting defects according to an embodiment of the present invention;and

FIG. 8 is a diagram schematically illustrating a system for fastinspecting defects according to an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The detailed explanation of the present invention is described asfollows. The described preferred embodiments are presented for purposesof illustrations and description, and they are not intended to limit thescope of the present invention.

The specimen hereafter described will be referred to wafer or reticle,wherein the reticle is used in lithography. Wafer may include siliconwafer, silicon-germanium wafer, SOI wafer, or III-V or II-VI compoundsemiconductor wafer. This invention can be also applied to reticleinspection, especially EUV mask inspection.

Referring to FIG. 3, a method for fast identifying defects according toan embodiment of the present invention includes scanning a specimen togenerate an original image and locations of regions of interest (S31)and reviewing the locations on the original image to identify defects(S32). In one embodiment, the scanning step is processed by using anE-beam inspection tool or an optical inspection tool. Also referring toFIG. 4, the scanned raw data is saved as an original image and stored ina storage device. In addition, the scanned raw data is also used foridentifying defects so as to identify locations of regions of interest.

In one embodiment, the scanned image is compared to the original designor predetermined patterns, such as GDS (Graphic Data System) or OASIS(open Artwork System Interchange Standard), or the scanned images arecompared to each other so as to obtain regions of interest. The regionsof interest include suspicious defects, real defects or criticalpatterns, wherein the suspicious defects include real defects andnon-defects. Referring to FIG. 5, the critical patterns, for example,may be referred as pitch of corners of traces 51 a, 51 b, connectionbetween traces 52 a, 52 b, pitch of traces 53 a, 53 b and connectionbetween trace 54 and electrode 55. In one embodiment, the regions ofinterest are obtained by following steps including identifyingsuspicious defects or critical patterns by using a firstimage-processing algorithm with a first set of parameters; identifyinghot spots according to the suspicious defects or the critical patterns;and marking locations of the hot spots. It is noted that the hot spotsmay include suspicious defects, real defects or critical patterns;alternatively, the hot spots may be an area that may be resulted in theabove-mentioned defects or an area having defect caused by theabove-mentioned defects.

It is noted that the original image stored in the storage device may bereviewed directly for further defect analysis without scanning specimensagain. In one embodiment, the same or different types ofimage-processing algorithm and parameters may be utilized for thereviewing the original image. For example, the reviewing step mayutilize the first image-processing algorithm with a second set ofparameters different from the first set of parameters; or the reviewingstep may utilize a second image-processing algorithm different from thefirst image-processing algorithm with the first set of parameters or thesecond set of parameters.

According to the above-mentioned, saving the scanned raw data as theoriginal image may save time for repeated scanning and prevent thedifference of scanning results caused by different scanning conditionsin the second scanning. In addition, the original image may bereproduced or divided for simultaneously performing a plurality ofdefect analysis so as to achieve shortened defect inspection time anddecreased false rate in defect inspection.

Referring to FIG. 6, a method for decreasing false rate in defectinspection according to one embodiment of the present invention includesproviding locations of regions of interest of a specimen by scanning asurface of the specimen (S61); saving scanned raw data as an originalimage (S62); and reviewing the locations on the original image toidentify defects on the surface (S63). According to the above-mentioned,the scanning step for scanning a surface of the specimen may beprocessed by using an E-beam inspection tool or an optical inspectiontool, and the types of algorithm and parameters used for identifyinglocations of regions of interest in the specimen and locations ofregions of interest in the reviewed original data may be the same ordifferent.

In one embodiment, the specimen may be a wafer including a plurality ofdies thereon, and the regions of interest are identified in one die ofthe plurality of dies. In the reviewing step, not only the locations ofregions of interest in the previously reviewed dies as well as otherlocations in addition to those are reviewed but all other dies on theoriginal image are reviewed. For example, in the case of finding a realdefect in one die, the correspondent locations in other dies in theoriginal image are also reviewed for identifying the similar defects inother dies.

Refer to FIG. 7, which illustrates a method for fast inspecting defectsaccording to one embodiment of the present invention. Firstly, a surfaceof a wafer is scanned by using an E-beam inspection tool or an opticalinspection tool (S71). Suspicious defects or critical patterns are thenidentified by using a first image-processing algorithm with a first setof parameters (S72). In addition, the scanned raw data from the scanningstep S71 is saved as an original image (S73). Hot spots according to thesuspicious defects or the critical patterns are then identified (S74),and locations of the hot spots are marked (S75). At last, the locationson the original image are reviewed to identify defects on the surface(S76).

Those skilled in the art of the present invention may understand how toanalyze the existence of specific defects in wafers by adopting specificimage-processing algorithm and parameters. Therefore, the original imagemay be reviewed with combination of the same or differentimage-processing algorithm and parameters for analyzing defects therein.In addition, the wafer also includes a plurality of dies on the wafer,and suspicious defects or critical patterns may be identified from oneof the plurality of dies. The locations of hot spots in the plurality ofdies and all other dies in the original images may be reviewed whenreviewing the original images.

A computer readable medium according to one embodiment of the presentinvention is encoded with a computer program. The computer program isconfigured for implementing the method for fast inspecting defects asillustrated in FIG. 7, wherein the detailed steps has been previouslymentioned and hence abbreviated herein.

Referring to FIG. 8, which illustrates a system 8 for fast inspectingdefects according to an embodiment of the present invention. The system8 is used for inspecting a sample 90 (such as a wafer) on a sample stage89 and comprises a charged particle beam generator 81, a condenser lensmodule 82, a probe forming objective lens module 83, a charged particlebeam deflection module 84, a secondary charged particle detector module85, an image forming module 86, a storage module 87 and a defectinspecting module 88.

The charged particle beam generator 81 is used for generating a primarycharged particle beam 801. The condenser lens module 82 is used forcondensing the generated primary charged particle beam 801. The probeforming objective lens module 83 is used for focusing the condensedprimary charged particle beam into a charged particle beam probe 802.The charged particle beam deflection module 84 is used for scanning theformed charged particle beam probe 802 across surfaces of the sample 90secured on the sample stage 89. In one embodiment, the charged particlebeam generator 81, the condenser lens module 82 and the probe formingobjective lens module 83, or their equivalent designs, alternatives orany combination thereof, together form a charged particle beam probegenerator which generates the scanning charged particle beam probe 802.

The secondary charged particle detector module 85 is used for detectingsecondary charged particles 803 emitted from the sample surface (mayalso be along with other reflected or scattered charged particles fromthe sample surface) upon being bombarded by the charged particle beamprobe 802 to generate a secondary charged particle detection signal 804.The image forming module 86 is coupled with the secondary chargedparticle detector module 85 for receiving the secondary charged particledetection signal 804 from the secondary charged particle detector module85 and forming at least one scanned raw image accordingly.

The image forming module 86 may be a mainframe host, terminals, personalcomputers, any kind of mobile computing devices or combination thereof.In addition, the image forming module 86 may connect with the secondarycharged particle detector module 85 through a medium selected from thefollowing: cable wire, optical fiber cable, portable storage media, IR,Bluetooth, intranet, internet, wireless network, wireless radio, and anycombination thereof. In one embodiment, secondary charged particledetector module 85 and image forming module 86, or their equivalentdesigns, alternatives or any combination thereof, together form an imageforming apparatus which forms a scanned raw image from detectedsecondary charged particles emitted from sample 90 being bombarded bythe charged particle beam probe 802. The storage module 87 is coupledwith the image forming apparatus and used for saving the scanned rawimage as an original image.

The above components of the system are well known to those skilled inthe art and are not presented here to limit the scope of the presentinvention. Alternatives and insubstantial modifications of thesecomponents should be construed equivalent to the disclosure of thepresent invention.

The defect inspecting module 88 is coupled to the image forming module86 of the image forming apparatus and the storage module 87 to inspectdefects on the sample 90 within the scanned raw image received from theimage forming module 86 and/or the original image received from thestorage module 87. In one embodiment, the defect inspecting module 88connects to and accesses the image forming apparatus and the storagemodule 87 through a medium selected from the following: cable wire,optical fiber cable, portable storage media, IR, manual input of humans,Bluetooth, intranet, internet, wireless network, wireless radio, and anycombination thereof. Further, the defect inspecting module 88 may beimplemented as one selected from the following: a mainframe host, aterminal computer, a personal computer, any kind of mobile computingdevices, and any combination thereof. In one embodiment, a computerprogram for fast inspecting defects is encoded on a computer readablemedium disposed within the defect inspecting module 88 so that thedefect inspecting module 88 is able to perform the steps of fastinspecting defects illustrated in conjunction with FIG. 7, wherein thedetails of the steps of fast inspecting defects is described earlier.

To sum up, the method and system for fast inspecting defects of thepresent invention saves scanned raw data as an original image so as tosave time for repeated scanning and achieve faster defect inspection andlower false rate by reviewing suspicious defects and other regions ofinterest in the original image by using the same or differentimage-processing algorithm with the same or different parameters.

While the invention is susceptible to various modifications andalternative forms, a specific example thereof has been shown in thedrawings and is herein described in detail. It should be understood,however, that the invention is not to be limited to the particular formdisclosed, but to the contrary, the invention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the appended claims.

What is claimed is:
 1. A system for fast inspecting defects, comprising:a charged particle beam probe generator for generating a chargedparticle beam probe; a charged particle beam deflection module fordeflecting the charged particle beam probe to scan across an area on asurface of a wafer, wherein the area includes one or more dies; an imageforming apparatus for detecting secondary charged particles emitted fromthe surface of the region of interest being bombarded by the chargedparticle beam probe and forming at least one scanned raw image of thearea accordingly; a storage module for saving the scanned raw image asan original image; a defect inspection module encoded with a computerprogram configured to cause the defect inspection module to identifydefects on the scanned raw image by using a first image-processingalgorithm with a first set of parameters; and provide a list oflocations on the scanned raw image that correspond to the defects forstoring; and a defect review module encoded with a computer programconfigured to cause the defect review module to review the locations onthe original image to analyze the defects on the surface by a firstdefect analysis that uses the first image-processing algorithm with asecond set of parameters different from the first set of parameters; anda second defect analysis that uses a second image-processing algorithmdifferent from the first image-processing algorithm, wherein the reviewof the locations on the original image comprises reproducing or dividingthe original image and simultaneously performing the first defectanalysis and the second defect analysis.
 2. The system according toclaim 1, wherein the wafer includes a plurality of dies thereon.
 3. Thesystem according to claim 2, wherein the defects are identified in onedie of the plurality of dies.
 4. The system according to claim 3,wherein the review of the locations on the original image comprises areview of the locations of each of the plurality of dies on the originalimage.
 5. The system according to claim 3, wherein the review of thelocations on the original image comprises a review of the locations ofeach of all other dies on the original image.
 6. The system according toclaim 1, wherein the wafer includes a plurality of dies and the defectson the at least one scanned raw image include locations at two or moreof the plurality of dies.
 7. The system according to claim 1, whereinthe original image is greater than or equal to 20 tera-bytes.